Mounting, in particular for disk spindles

ABSTRACT

In a mounting for disk spindles, an embodiment is provided in which, despite simple construction and simple assembly of the bearing, a high degree of precision is obtained. The angle ball bearings in O-arrangement have outer rings (4) the race (4&#39;) of which has, in longitudinal section, a radius the center point (7) of which lies on the axis of rotation (8) of the inner races (2).

The present invention relates to a mounting for disk spindles,particularly to two angle ball bearings clamped spaced apart on a shaft,a nd particularly to minimizing the effect of non-parallel alignment ofthe outer ring races of the bearings a bearing.

Mountings for disk spindles have been known and used for many years(see, for instance, SKF Kugellagerzeitschrift 232, 4/1988). Up to nowembodiments have always been selected in which two deep-groove ballbearings or two angular ball bearings are arranged on the shaft at acertain distance apart and are clamped axially with respect to eachother so that the desired freedom from play is obtained. Since smallerdisks and disks of higher storage capacity are constantly beingdeveloped, it has been necessary to increase the precision of themountings. Therefore, the bearings of the spindles were improved by, forinstance, by including fewer structural parts and/or having fewerfitting and joining surfaces also. One improvement was that specialinner rings were avoided by arranging the travel path of the ballsdirectly in the shaft. Assembly-produced tilting with respect to eachother of the inner-ring races was thereby excluded. The parallelalignment of the outer-ring races is also a prerequisite for optimalrolling conditions in the bearing. However, because of the tolerances inthe fitting and joining surfaces of the outer rings, completely parallelalignment of the outer-ring races with respect to each other cannot beachieved. This has produced variations in the pressure angle in thecircumference of the race which have a negative effect on the rollingconditions and thus on the precision of the mounting.

The object of the invention is to develop the aforementioned bearings soas to obtain high precision despite simple construction and simpleassembly of the bearings.

The two bearings, which are clamped axially with respect to each other,are similar to two angular contact ball bearings. However, due to thefact that their races form sections of spherical surfaces with thecenter point on the axis of rotation, tilting of the outer rings withrespect to each other is possible without variations in pressure angleoccurring around the circumferential direction of the race. This is animportant condition for high precision of the bearing. Due to the factthat the resultant pressing force of the compression spring does not actconcentrically to the outer rings, the outer rings tilt in the bore ofthe sleeve.

If the distance between one axial end surface of the outer ring and thepoint of intersection of the pressure line of the bearing balls on theaxis of rotation is made the same size as the distance between thatpoint of intersection and the other end surface of the bearing,self-centering of the longitudinal axis of the bearing in the bore ofthe sleeve is obtained. Thus, the slot width between the outer rings andthe sleeve has no effect on the central seating of the outer rings inthe bore of the sleeve. The manufacturing tolerances for the sleeve boreand outer-ring diameter can be larger. The gaps produced between theouter rings and the sleeve bore are then filled with an adhesive whichhardens. In this way, movements between the outer rings and the sleeveare avoided.

Despite obtaining maximum precision of the bearing, parallel alignmentof the outer rings to each other and centering of the outer rings in thebore of the sleeve is therefore no longer necessary here.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be explained further with reference to the drawingwhich is a longitudinal section through the mounting of a disk spindle.

Referring to the drawing, the mounting comprises a shaft in which thereare worked the inner races 2 for two angle ball bearings, each bearingcomprising a row of balls 3, of the outer ring 4 for the row of ballsand a sleeve 5 around the outer ring. Between the outer rings 4, whichare spaced apart from each other, there is a compression spring 6 whichclamps the outer rings axially with respect to each other and urges theouter rings apart. Therefore, each bearing ball row is pressed axiallyoutward from the other row and against the axially outward region of therespective inner race.

In accordance with the invention, the race 4' of each outer ring 4 is soprofiled that it forms a partial spherical surface, the center point 7of the radius lying on the longitudinal axis of rotation 8 of the innerraces 1'. In this way, tilting of either or both of the outer rings 4 inthe sleeve 5 is possible without changes in pressure angle occurring,since, in every position of tilt, the balls 3 are always opposite thesame spherical surface. Upon assembly, an adhesive is introduced intothe gaps 9 produced by the tilting of either outer rings, the adhesivethen hardening and fixing the outer rings 4 in position in the sleeve 5.

The pressure lines 7 from all of the balls in each of the bearings aredirected both radially inwardly and axially outwardly by the races ofthe outer ring and the force of the spring 6 on that ring. If thedistance 11 between the one end surface 10 of the outer rings 4 and thepoint of intersection 7 of the pressure lines on the axis 8 is madeequal to the distance l₂ between the point of intersection 7 and theother end surface 11 of the outer rings 4, self-centering of the axis ofrotation (8) takes place within the bore of the sleeve 5. In this way,the influence of manufacturing tolerances on the precision of themounting is eliminated.

I claim:
 1. A mounting for a disk spindle, comprising a shaft, twoaxially spaced apart angular ball bearings on the shaft, means clampingthe ball bearings axially apart on the shaft;each ball bearingcomprising a row of bearing balls around the shaft, an inner racedefined in the shaft for the balls in a row and an outer ring includingan outer face around the row of balls; each outer race being shapedalong a longitudinal section thereof to have a radius which liesapproximately on the axis of rotation of the shaft and the outer racesbeing free to tilt around the center point of the surface of the raceunder the influence of the clamping means.
 2. The mounting of claim 1,further comprising a sleeve around the outer rings and spaced therefromto enable tilting of the outer rings with respect to the shaft under theinfluence of the clamping means.
 3. The mounting of claim 2, furthercomprising means for fixing the tilt orientation of the outer rings inthe sleeve once the tilt orientations are set by the clamping means. 4.The mounting of claim 2, wherein the clamping means urge the outer ringsaxially apart.
 5. The mounting of claim 4, wherein the inner races areshaped to oppose movement axially apart of the outer rings by means ofthe outer rings engaging the respective rows of bearing balls for urgingthe rows of bearing balls axially apart while the inner races opposeaxially outward movement of the rows of bearing balls, the rows ofbearing balls having resultant lines of pressure which develop from theaction of the clamping means;the outer rings each having axiallyopposite end surfaces; the outer ring is so shaped and the outer racethereof is so shaped that a first distance between one of the endsurfaces of each outer rings and the point of intersection of thepressure lines of the respective row of bearing balls in the axis ofrotation is equal to a second distance between the other end surface ofthat outer ring and the same point of the intersection of the pressurelines of the respective row of bearing balls on the axis of rotation. 6.The mounting of claim 5, wherein each outer race is a partial spheresuch that the outer ring may tilt.
 7. The mounting of claim 6, the outerrace partial sphere has a center on the point of intersection of thepressure lines of the respective row of bearing balls on the axis ofrotation.